1. Field of the Invention
The present invention relates generally to liquid-solid separators, and more specifically to juice processing and dejuicing equipment.
2. Description of the Prior Art
The production of fruit and vegetable juices typically includes the steps of the crushing of the fruit, the separating of the resultant juice from the pulp, and the further processing of the juice. Depending on the particular application, that intermediate step of separating the juice from the pulp is accomplished in various ways. In the wine industry, for example, after the grapes have been crushed, the pulp and juice "mash" is often pumped through a mash line to a drain tank or other unit to remove the easily accessible "free run" juice, before sending the remainder to a wine press for final juice extraction. Because of the costs associated with operating a press, it is desirable to maximize the amount of free-run juice, and minimize the use of the press.
However, the use of a drain tank itself has serious drawbacks. For example, while drain tanks are generally less expensive than presses, neither are inexpensive. Also, drain tanks occupy a large amount of space, and may require an expensive support structure for proper operation. Furthermore, the loading of the mash into and the unloading of the dejuiced mash from a drain tank can be difficult. In addition, stationary drain tanks are relatively inefficient since there is usually no provision for increasing mass transfer, while non-stationary drain tanks are more expensive and prone to mechanical difficulties due to the drive motors, bearings, and the like necessary to drive the tank. Still further, except for the weight in the drain tank of the mash itself, there is no provision for low pressure pressing of the mash during draining. Finally, the amount of juice drainage surface area in a drain tank is limited and competes with the drain tank volume.
Some dejuicing devices have been developed in an effort to reduce or eliminate drain tank requirements. For example, one device currently in use provides an inclined sheet of stainless steel, perforated by numerous small, circular holes over which a "ladder conveyor" passes. Mash is dragged across this surface and juice exits through the holes, while dejuiced mash is dragged up the incline and dumped into a press. However, this device allows significant exposure of and oxidation to the moving mash, and creates undesirable shearing forces to the mash all along the drag screen surface, particularly on the upper edges of the drain holes. Other devices have replaced the circular holes with elongated slots, which tends to reduce, but not eliminate, the shear forces on the mash, and of course do nothing to prevent oxidation of the mash.